So called conservation compliance tillage implements which contain both disc gangs and deep tillage shanks are presently commercially available. Generally speaking, the discs, which are positioned ahead of the shanks, are arranged in oblique gangs at a relatively shallow depth for trash severance and topsoil tilling while the shanks are disposed for deep penetration into the subsoil to remove lower compaction zones and provide subsoiling slots that encourage the entry and penetration of moisture. The discs, which are concavo-convex, slice through the crop residue on the surface of the field while turning the topsoil and mixing the severed residue down below ground level to speed up decomposition for enrichment of the soil while leaving a portion of the residue above ground to reduce wind and water erosion. Since the discs are arranged in gangs which extend at oblique angles with respect to the path of travel of the machine, they throw soil inwardly or outwardly depending upon their orientation, which contributes to residue coverage. Ideally, the angle of attack of the disc gangs can be adjusted to increase or decrease the amount of soil which is thrown by the discs, thereby adjusting the amount of residue coverage which is achieved.
Desirably, in some models the pairs of disc gangs are arranged in tandem, with one oppositely outwardly extending pair of gangs disposed in leading relationship to the other. The gangs of the forward pair normally converge rearwardly as the centerline of the machine is approached to present a general V-shape when the implement is viewed in plan, while the gangs of the trailing pair converge forwardly as the center of the machine is approached to present an inverted V-formation when the machine is viewed in plan. The discs of the forward pair of gangs are disposed to throw the soil outwardly in opposite directions from the center of the machine, while the discs of the rear pair are disposed to throw it back inwardly.
It is desirable to be able to change the depth of the shanks relative to the depth of the discs, and vice versa, to accommodate different soil conditions and personal preferences. However, prior adjustment arrangements have not been satisfactory in this respect.
For example, a disc-ripper commercialized by Sunflower Manufacturing Company, Inc., of Beloit, Kansas, and illustrated in a brochure identified as BAC 9401/2/89, employs hydraulic mechanism for raising and lowering a set of ripper shanks at the rear of the machine, which mechanism necessarily involves considerable expense and complexity. Although the disc gangs can apparently be angle-adjusted in a fore-and-aft sense, there is no means provided for varying the depth of the gangs relative to the frame itself.
Similarly, a Model 435 Conservation Chisel Plow of White Farm Equipment disclosed in a sales brochure 15M82 Form No. S274 utilizes a hydraulic system for depth adjustment. In that machine, a series of discs are mounted on a tool bar across the front of the machine which bar is raisable and lowerable by a hydraulic piston and cylinder assembly. In this unit the discs, while individually disposed at oblique angles relative to the path of travel of the machine, are not mounted on beams which are themselves disposed obliquely with respect to the path of travel of the machine. Thus, this arrangement lacks the advantages of angularly arranged disc gangs, as well as tandemly arranged gangs, and provides no means for angle adjustment.